Method of and apparatus for conveying granular masses in tubular treating chambers

ABSTRACT

Solid fuel, such as granular raw brown coal, is moved through an approximately horizontally disposed tubular heat treating chamber (reaction tube) by means of a carrier fluid, the flow of which is periodically interrupted or at least decreased by periodically closing a fluid discharge valve disposed downstream of the reaction tube. During the closed periods of the valve, at least one part of the granular material settles in the tube and, when the valve is opened, the matrial is rendered turbulent by the initial thrust of the carrier fluid as the latter resumes its periodic effective flow.

United States Patent [191 Wenzel et al.

[73] Assignees: Rheinische Braunkohlenwerke AG, Cologne; Werner Wenzel,Aachen, th ffi rm [22] Filed: Apr. 2, 1971 1211 Appl. No.: 130,701

[30] Foreign Application Priority Data Apr. 2, 1970 Germany P 20 15791.9

[52] US. Cl 432/15, 302/26, 432/58,

[51] Int. Cl .f. 365g 53/04 [58] Field of Search 34/10, 57 R, 57 B;263/21 R, 21 A; 302/17, 52, 59, 26; 432/15,

145 Aug.7, 1973 [56] References Cited Primary Examiner-John .1. CambyAssistant Examinerl-lenry C. Yuen Att0rneyEdwin E. Greigg [57] ABSTRACTSolid fuel, such as granular raw brown coal, is moved through anapproximately horizontally disposed tubu lar heat treating chamber(reaction tube) by means of a carrier fluid, the flow of which isperiodically interrupted or at least decreased by periodically closing afluid discharge valve disposed downstream of the reaction tube. Duringthe closed periods of the valve, at least one part of the granularmaterial settles in the tube and, when the valve is opened, the matrialis rendered turbulent by the initial thrust of the carrier fluid as thelatter resumes its periodic effective flow.

14 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION This inventionrelates to the transport of a granular mass in a reaction tube in whichsaid mass is submitted to a heat treatment by virtue of the externallyheated hot tube walls.

In known heat treating apparatuses of the aforeoutlined type, thegranular mass is moved within the tubes by mechanical conveying means,such as worms, chains, and the like, or, the tube is disposed at anangle to the horizontal and is rotated about its horizontal axis or anaxis intersecting the latter. It has also been proposed to move thegranular mass through the tube by means of a fluid carrier.

These known means for moving the granular mass through the reaction tubehave various disadvantages which exclude, or at least make difficult,their use in a number of important processes. These difficulties residein the fact that on occasions the necessary mechanical equipment forconveying the granular mass through tubes is too complex or requires toomuch space to be usable in the relatively small-diameter reaction tubes.The difficulty inusing a conveying fluid medium, such as a gas or aliquid, lies in the necessity of driving the fluid medium withrelatively large speeds, in order to prevent, particularly in case ofcarrier gases, the granular material from settling on the inner wall ofY the tubes. I

The invention is based on a method and apparatus for the transport of agranular mass in horizontal or slightly inclined tubes or tubularsections in which a gaseous or liquid conveying medium is used.

OBJECTS, SUMMARY AND ADVANTAGES OF THE INVENTION It is an object of theinvention to provide an improved method and an apparatus for theaforeoutlined type wherein the known disadvantages and difficulties areeliminated.

It is also an object of the invention to provide an improved method andan apparatus of the aforeoutlined type wherein the dwelling time of thegranules in the reaction tube may be arbitrarily controlled.

Briefly stated, according to the invention, the advancing speed of thefluid carrier is caused to periodically alternate between a high and alow value in such a manner that during the low-speed fluid advance, thegranular mass settles partially or entirely on the tube wall, whereasduring the high-speed fluid flow, it is entirely or substantially in itsentirety carried away by the fluid medium.

It is an advantage of the 'aforenoted method that the granular mass maybe conveyed through long tubes without taking addtional steps to obtainsuch result. It is-a further advantage that larger granules have alonger dwelling time in the reaction tube than smaller ones. In thismanner there is an automatic matching of the conveying speed with theduration of dwelling time during which the granules, as a function oftheir size, have to be exposed to the heat treatment in the reactiontube.

The invention will be better understood, as well as further objects andadvantages will become more apparent, from the ensuing detailedspecification of a preferred, althoughexemplary, embodiment of theinvention taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side elevationalview of the preferred embodiment including a horizontally arrangedreaction tube and FIG. 2 is a schematic side elevational view of thesame embodiment including a slightly inclined reaction tube.

GENERAL CHARACTERISTICS OF THE METHOD ACCORDING TO THE INVENTION Thespeed of the carrier fluid passing through the reaction tube may bealtered, for example, by periodically interrupting the entry of thefluid into the tube. It is also feasible to periodically interrupt theoutflow of the carrier fluid at the discharge end of the tube.

It has been found to be particularly advantageous for reasons givenhereinafter to reduce the speed of the carrier fluid slowly, but toincrease its speed rapidly. In this manner the resumption of the fluidflow starts with a thrust. For thispurpose, at the charging end of thetube where the granular mass to be treated is introduced, there may beprovided an inlet controlling means for the conveying fluid. Thiscontrolmeans is periodically opened and closed (fully or partially) insuch a manner that the opening occurs relatively rapidly and arelatively large flow passage section is made available for the fluidmedium so-that, as mentioned hereinbefore, the medium may resume itstravel through the tube with an'initial thrust in the direction of itsdischarge end. Such an initial thrust causes a sudden turbulence andthus a spontaneous stirring of the granular mass which is subsequentlycarried by the fluid medium in the direction of the discharge end of thetube. After a short while the inlet control means is again closed, atleast to such an extent that the granular mass or at least a desired ordeterminable quantity thereof again settles on the tube walls whileanother,

fine-grain portion of the granular mass, is displaced by theslow-flowing carrier fluid.

According to a further embodiment of the novel method, the carrier fluidis introduced into the tube continuously or intermittently at one ormore locations and at the discharge end of the tube there is provided,for controlling the outlet of the carrier fluid, a valve means, such asa gate or a plug, which is intermittently opened and closed. During theclosed condition of the valve means, in the reaction tube a pressurebuildup takes place which, upon opening of the valve means, leads to thethrustlike resumption of the rapid fluid flow from the charging end ofthe tube to the outlet end thereof. It is expedient to operate the inletcontrol means for the carier fluid synchronously with the valve meanstherefor at the outlet end of the reaction tube. In general, it issufficient if the inlet valve is maintained continuously open with arelatively small flow passage section so that during the closedcondition of the outlet valve means a slow buildup of pressure may takeplace in the reaction tube.

An important field of application of the method according to theinvention is in vaporizing processes, gasiflcation processes andchemical reactions for granular masses which for these purposes are tobe heated in a tubular system. The aforenoted or similar processes maytake place in the same tube in succession or in an overlapping manner.

As the raw material, such as water-containing granular raw brown coal,is introduced by a charging mechanism into the reaction tube, it isfirst thoroughly dried by the heat applied by the tube wall. As aresult, water vapor escapes from the raw material and serves as thecarrier fluid for transporting the material in the reaction tube.Subsequent to the drying of the raw brown coal, the dry coal is, byvirtue of further heating, gas ified whereby further conveying gases aregenerated. As the dry coal is conveyed according to the invention, it iseventually heated by the tubular walls to such an extent that it reactswith the water vapor constituting the conveying medium and with thecarbon dioxide obtained from the gasification of the coal and therebycombustible gases are generated.

According to the invention, the coal periodically settles in the tube asthe carrier fluid slows down. In this manner the granules contact thehot tube wall, and, as a result, an intensive heating thereof occurs. Byvirtue of the subsequent stirring of the coal caused by the opening ofthe outlet means for the carrier gas, the coal heated to the greatestextent in the vicinity of the tube wall will vigorously contact thewater vapor and the carbon dioxide to thus induce the desiredgasification reactions. Upon the resettling of the solid granules fromthe carrier gas as the gas outlet means is closed, continuously new andcolder coal particles contact the hot tube wall, so that the conveyingmethod according to the invention simultaneously functions as anessential measure for the rapid heating of the entire coal contents inthe reaction tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT FOR PRACTICING THE METHODACCORDING TO THE INVENTION Turning now to FIG. 1, there is shown ahorizontally disposed reaction tube 1, to the charging end of whichthere is fixedly secured a gastight storage chamber 3 which holds agranular mass of water-containing raw brown coal or similar material tobe gasified. Within the storage chamber 3 there is provided a chargingdevice for introducing the raw material into the reaction tube 1. Thecharging device comprises a shovel 4 rotatable by a shaft 5 securedthereto and disposed in alignment or parallel with the axis of tube 1.The rotatable shaft 5 traverses the wall of the storage chamber 3through a fluidtight bushing 6 to be driven externally by power means(not shown). Above the chamber 3 there is disposed a charging container7 and a gastight dispensing wheel 8 for introducing the granular rawmaterial into the chamber 3.

For providing the necessary heat for the treatment of the granularmaterial in the reaction tube 1, the walls thereof are externally heatedby a heat carrying medium passed through a heating chamber 20surrounding the reaction tube 1 and comprising an outer casing 21 aswell as an inlet port 22 and an outlet port 23 for the admission andwithdrawal of a heating medium.

At the downstream or outlet end of the reaction tube 1 there is provideda separation chamber 9 in which the residues 10 are accumulatedsubsequent to the gasification process. The container 9 may be,downwardly emptied by a gas-tight dispensing wheel 11. From the chamber9 there also extends a gas conduit 12 through which the gas generated inthe reaction tube 1 may be taken out. In order to maintain the pressurein the gasification system at a desired value, the gas conduit 12 isprovided with an adjustable outlet valve 13. From the chamber 9 thereextends a further gas conduit 15 in which there is disposed a fluiddischarge valve 14 which, according to the invention, is periodicallyopened and closed. When the discharge valve is closed,

- at least one part of the conveyed granular mass will settle in theentire reaction tube as indicated at 16 in the tube portion 1a. When thefluid discharge valve 14 is opened, the gas flow in the reaction tube 1resumes with an initial, spontaneous thrust in the direction of thereceiving container 9. In this manner the settled coal is renderedturbulent and is thus vigorously stirred. The granular material isillustrated in this turbulent condition in tube portion 1b and is giventhe reference numeral 17.

Turning now to FIG. 2, the apparatus shown therein differs from FIG. 1only in that the reaction tube slopes downward in the downstreamdirection. It is noted that the components corresponding to those shownin FIG. 1 are designated with reference numerals increased by 100. Theangle 102 which the reaction tube forms with the horizontal depends uponthe size, shape and surface properties of the granules, the desiredconveying speed thereof and the surface properties of the tube wall. Thesaid angle is usually between 5 and 20 and is generally so adjusted thatin the absence of a flow of the carrier fluid, no spontaneous sliding ofthe granular mass occurs. Such spontaneous sliding is disadvantageoussince, in the first place, it cannot be controlled and may easily leadto clogging of the tube and, secondly, it is not selective with regardto the grain sizes. Thus, the inclined positioning of the reaction tubeaids, but does not cause the motion of the granular mass.

It is an advantage of the above-described horizontal or approximatelyhorizontal, but non-rotary reaction tube structure that a gastight jointwith the upstream and downstream chambers may be effected in a simplemanner.

OPERATION OF THE PREFERRED EMBODIMENT In the description that followsthe reference numerals will be those of FIG. 1 and it is to beunderstood that the same reference numerals increased by apply to theembodiment shown in FIG. 2.

The charging container 7 is filled, for example, with small-grain rawbrown coal 19 of grain sizes between 0 and 5 millimeters. This granularmass is continuously or intermittently fed into the stroage chamber 3 bymeans of heated the dispensing wheel 8. By setting the dispensing wheel8 to an appropriate feeding speed, there is maintained a raw coal layer18 in the storage chamber 3. As the shovel 4 rotates, it dips into thecoal layer 18 and feeds quantities thereof into the reaction tube 1. Thetube walls heated by the heating medium flowing through heating chamber20 heat the granular raw brown coal mass which, as a result, releaseswater vapor. The gas outlet valve 13 is so adjusted that in the entiregasification system which comprises the storage chamber 3, the reactiontube 1 and the separation chamber 9, the vapor pressure is adapted toexceed a value of approximately 2 kg/cm. As soon as this pressure isreached during the course of a pressure buildup, the discharge valve 14is automatically opened to provide, for a short period of time, a flowpassage section of such an extent that a rapid drop of the gas pressureoccurs in the system as the gas escapes through the open valve 14 andthe outlet conduit 15. The depressurization of the separation chamber 9causes a gas thrust along the reaction tube 1 in the direction of thechamber 9. By virtue of the gas surge, the granular coal which hassettled in the reaction tube 1 in the absence of a carrier gas flow, isstirred and conveyed in the di rection of the separation chamber 9.Thus, the vapor, escaping through the open discharge valve 14, functionsas a carrier fluid as it displaces the granular mass in the reactiontube 1. When due to the release of the vapor through the discharge valve14, the pressure in the separation chamber 9 drops to a value of forexample 0.2 kg/cm the discharge valve 14 is closed. In this manner thegas flow in the direction of the discharge end of the reaction tube 1 isagain decreased so that the granular coal or the granular residuesthereof may again settle in the tube as the gasification processprogresses. As soon as the discharge valve 14 is closed, again apressure buildup takes place and again, upon reaching the predeterminedpressure value of, for example, 2 kg/cm the discharge valve 14 is openedand the aforedescribed cycle is repeated. The distance through which thecarrier fluid displaces the material in the reaction tube during onecycle of fluid flow, depends on the magnitude of the pressure drop inthe separation chamber 9 as well as on the duration of the opencondition of the discharge valve 14 and thus on the duration of theinitial surge. The invention permits different variations andadaptations to be effected in given processes. Such variations mayparticularly include the coal charging devices and the slag removingmechanisms.

A significant variant of the apparatus resides in dimensioning thestorage chamber 3 in such a manner that the thrust of fluid from chamber3 into the reaction tube 1 during the depressurization of the systemcontributes to the conveying of the material in the reaction tube. It isnoted that with proper dimensioning of the coal charging device, duringthe phase of the pressure buildup in the reaction tube, one part of thewater vapor obtained from the raw coal in the reaction tube flowstowards the storage chamber 3 against the motion of the coal. Upondischarging the system as a result of opening the valve 14, one part ofthe vapor accumulated in the storage chamber 3 may be taken out from thesystem through a vapor outlet valve provided for this purpose at theupper portion of the storage chamher 3.

The utilization of the method and apparatus according to the inventionin the gasification process of raw brown coal is particularlyadvantageous. The advantage lies particularly in the fact that withsimple means and without complex equipment a very efficient gasificationmay be achieved with a wide selection of the heating media. The lattermay be exhaust gases or may be molten metal heated by the coolant of anuclear reactor.

It is another important advantage of the aforedescribed preferredembodiment that the carrier fluid does not have to be introduced from anexternal source: it is generated within the, reaction tube and isconstituted by the water vapors released by the brown coal upon heating.It is to be understood that in addition to or instead of the water vaporgenerated during the gasification process, a carrier fluid taken from anexternal source and introduced into the reaction tube may also be used.

That which is claimed is:

1. In a method for conveying granular material through a horizontal orslightly inclined tube by means of a carrier fluid flowing therethrough,the improvement comprising the steps of: heating at least a portion ofthe external wall of said tube thereby subjecting said material to aheat treatment; and periodically varying the speed of said fluid betweena high speed level and a low speed level, at least a substantial part ofsaid material settles in said tube during the low-speed fluid flow andat least a substantial part of said material is conveyed by said fluidduring the high-speed fluid flow.

2. A method as defined in claim 1, wherein the variation of the fluidspeeds is effected by periodically interrupting the inflow of said fluidinto said tube.

3. A method as defined in claim 1, including the step of causing saidfluid to being each high-level speed period with an initial thrust.

4. In a method for conveying granular material through a horizontal orslightly inclined tube by means of a carrier fluid flowing therethrough,the improvement comprising the step of: periodically varying the speedof said fluid between a high speed level and a low speed level byperiodically interrupting the outflow of said fluid ata discharge end ofsaid tube, at least a substantial part of said material settles in saidtube during the low-speed fluid flow and at leasta substantial part ofsaid material is conveyed by said fluid during the high-speed fluidflow.

5. A method as defined in claim 4, wherein each interruption of saidoutflow is effected relatively slowly and each resumption of saidoutflow is effected relatively rapidly.

6. In a method for conveying granular material through a horizontal orslightly inclined tube by means of a carrier fluid flowing therethrough,the improvement comprising the step of: periodically varying the speedof said fluid between a high speed level and a low speed level byperiodically interrupting the outflow of said fluid at a dischage end ofsaid tube synchronously with a periodic interruption of the inflow ofsaid fluid into said tube, at least a substantial part of said materialsettles in said tube during the low-speed fluid-flow and at least asubstantial part of said material is conveyed by said fluid during thehigh-speed fluid flow.

7. In a method for conveying granular material through a horizontal orslightly inclined tube by means of a carrier fluid flowing therethrough,the improvement comprising the steps of: periodically varying the speedof said fluid between a high speed level and a low speed level, at leasta substantial part of said material settles in said tube during thelow-speed fluid flow and at least a substantial part of said material isconveyed by said fluid during the high-speed fluid flow; and effecting abuildup of pressure of said fluid in said tube during each period oflow-speed fluid flow, said pressure causing said fluid to resume eachperiod of highspeed fluid flow with an initial thrust.

8. In a method for. conveying granular material through a horizontal orslightly inclined tube by means 7 of a carrier fluid flowingtherethrough, the improvement comprising the steps of: periodicallyvarying the speed of said fluid between a high speed level and a lowspeed level, at least a substantial part of said material settles insaid tube during the low-speed fluid flow and at least a substantialpart of said material is conveyed by said fluid during the high-speedfluid flow; and generating said carrier fluid within said tube bysubmitting said material to a heat treatment.

9. A method as defined in claim 8, wherein said carrier fluid is watervapor obtained from said material in said tube. a

10. A method as defined in claim 9, wherein said material iswater-containing coal, more particularly raw brown coal, said methodincluding the step of heating said tube to temperatures for effecting adrying of said coal and its decomposition and gasification with watervapor.

11. An apparatus for conveying granular material by means ofperiodically varying the speed of a carrier fluid in the apparatusbetween a high speed level and a low speed level, comprising:

A. an approximately horizontal tube having an inlet and an outlet,

B. means for externally heating said tube,

C. fluidtight feeding means attached to said inlet end of said tube andD a closing means disposed downstream of said outlet of said tube, withthe arrangement of elements (A) through (D) being such that at least asubstantial pan of the material settles in said tube during thelow-speed fluid flow and at least a substantial part of the material isconveyed by said fluid during the high-speed fluid flow.

12. An apparatus as defined in claim 1 1, wherein said fluidtightfeeding means includes a feeding screw.

13. An apparatus as defined in claim 1 1, wherein said closing means isformed as a gate for blocking the cross section of said tube.

14. An apparatus as defined in claim 11, wherein said tube extendslinearly,

1.! i i l

1. In a method for conveying granular material through a horizontal orslightly inclined tube by means of a carrier fluid flowing therethrough,the improvement comprising the steps of: heating at least a portion ofthe external wall of said tube thereby subjecting said material to aheat treatment; and periodically varying the speed of said fluid betweena high speed level and a low speed level, at least a substantial part ofsaid material settles in said tube during the low-speed fluid flow andat least a substantial part of said material is conveyed by said fluidduring the high-speed fluid flow.
 2. A method as defined in claim 1,wherein the variation of the fluid speeds is effected by periodicallyinterrupting the inflow of said fluid into said tube.
 3. A method asdefined in claim 1, including the step of causing said fluid to begineach high-level speed period with an initial thrust.
 4. In a method forconveying granular material through a horizontal or slightly inclinedtube by means of a carrier fluid flowing therethrough, the improvementcomprising the step of: periodically varying the speed of said fluidbetween a high speed level and a low speed level by periodicallyinterrupting the outflow of said fluid at a discharge end of said tube,at least a substantial part of said material settles in said tube duringthe low-speed fluid flow and at least a substantial part of saidmaterial is conveyed by said fluid during the high-speed fluid flow. 5.A method as defined in claim 4, wherein each interruption of saidoutflow is effected relatively slowly and each resumption of saidoutflow is effected relatively rapidly.
 6. In a method for conveyinggranular material through a horizontal or slightly inclined tube bymeans of a carrier fluid flowing therEthrough, the improvementcomprising the step of: periodically varying the speed of said fluidbetween a high speed level and a low speed level by periodicallyinterrupting the outflow of said fluid at a dischage end of said tubesynchronously with a periodic interruption of the inflow of said fluidinto said tube, at least a substantial part of said material settles insaid tube during the low-speed fluid flow and at least a substantialpart of said material is conveyed by said fluid during the high-speedfluid flow.
 7. In a method for conveying granular material through ahorizontal or slightly inclined tube by means of a carrier fluid flowingtherethrough, the improvement comprising the steps of: periodicallyvarying the speed of said fluid between a high speed level and a lowspeed level, at least a substantial part of said material settles insaid tube during the low-speed fluid flow and at least a substantialpart of said material is conveyed by said fluid during the high-speedfluid flow; and effecting a buildup of pressure of said fluid in saidtube during each period of low-speed fluid flow, said pressure causingsaid fluid to resume each period of high-speed fluid flow with aninitial thrust.
 8. In a method for conveying granular material through ahorizontal or slightly inclined tube by means of a carrier fluid flowingtherethrough, the improvement comprising the steps of: periodicallyvarying the speed of said fluid between a high speed level and a lowspeed level, at least a substantial part of said material settles insaid tube during the low-speed fluid flow and at least a substantialpart of said material is conveyed by said fluid during the high-speedfluid flow; and generating said carrier fluid within said tube bysubmitting said material to a heat treatment.
 9. A method as defined inclaim 8, wherein said carrier fluid is water vapor obtained from saidmaterial in said tube.
 10. A method as defined in claim 9, wherein saidmaterial is water-containing coal, more particularly raw brown coal,said method including the step of heating said tube to temperatures foreffecting a drying of said coal and its decomposition and gasificationwith water vapor.
 11. An apparatus for conveying granular material bymeans of periodically varying the speed of a carrier fluid in theapparatus between a high speed level and a low speed level, comprising:A. an approximately horizontal tube having an inlet and an outlet, B.means for externally heating said tube, C. fluidtight feeding meansattached to said inlet end of said tube and D. a closing means disposeddownstream of said outlet of said tube, with the arrangement of elements(A) through (D) being such that at least a substantial part of thematerial settles in said tube during the low-speed fluid flow and atleast a substantial part of the material is conveyed by said fluidduring the high-speed fluid flow.
 12. An apparatus as defined in claim11, wherein said fluidtight feeding means includes a feeding screw. 13.An apparatus as defined in claim 11, wherein said closing means isformed as a gate for blocking the cross section of said tube.
 14. Anapparatus as defined in claim 11, wherein said tube extends linearly.